A device for controlling a wiper motor is described in German patent DE 33 14 770 C2. The device includes an optoelectronic sensor apparatus and a circuit arrangement connected to the drive motor, so that control of the drive motor my be effected in dependence upon the coating present on the windshield.
The 33 14 770 C2 device does not, however, comprise any means allowing detection of the last sweep process of a wiping cycle which effects a last cleaning of the measuring range of the sensor apparatus. Thus, the device may indeed to some extent satisfactorily adapt the wiping cycle frequency automatically to quantitative changes arising during wiper operation in the condition of the coating on the windshield, such as, for example, the degree of dirt accumulation, the quantity of rain or snow striking the windshield. However, it is not possible satisfactorily to achieve precise automatic adaptation of the wiping cycle frequency to both qualitative and quantitative changes in the condition of the coating on the windshield.